Topological Surface States of Dirac Fermions in n-Bi2Te3 –ySey Thermoelectrics

Semiconductors - In n-Bi2Te3 and n-Bi2Te3 –ySey thermoelectrics, the surface states of Dirac fermions of the interlayer Van der Waals surface (0001) are studied by scanning tunneling...     

Enhancement of Spin–Orbit Interaction by Bandgap Engineering in InAs-Based Heterostructures

We investigated Rashba spin–orbit interaction in various InAs-based heterostructures to evaluate the relative significance of the electric field in the quantum wells (QWs) and at the interfaces. Test structures were designed in such a way that the peak of the electron wave function was located on the abrupt band discontinuity at the front end of the main channel, whereas a control sample had no band discontinuity in the middle of the QW. The Rashba coefficient obtained for the test structures was almost double that of the control sample. Significant contribution of the electric field at the band discontinuity was verified by k · p calculation. Bandgap engineering was shown to be effective for obtaining an increased Rashba coefficient.     

Ultra-Damping Composites Enhanced by Yolk–Shell Piezoelectric Damping Mechanism

High-performance damping materials are significant toward reducing vibration and maintaining stability for industrial applications. Herein, a yolk–shell piezoelectric damping mechanism is reported, which can enhance mechanical energy dissipation and improve damping capability. With the addition of yolk–shell particles and carbon nanotube (CNT) conductive network, damping properties of various resin matrices are enhanced with the energy dissipation path of mechanical to electrical to heat energy. Particularly, the peak loss factor of epoxy composites reaches 1.91 and tan δ area increases by 25.72% at 20 °C. The results prove the general applicability of yolk–shell piezoelectric damping mechanism. Besides, the novel damping materials also exhibit excellent flexibility, stretchability, and resilience, offering a promising application toward damping coating, indicating broad scope of application in transportation and sophisticated electronics, etc.     

Enhancement of Spin–Orbit Torque by Strain Engineering in SrRuO3 Films

Complex oxides with 4d/5d transition metal ions, e.g., SrRuO₃, usually possess strong spin–orbit coupling, which potentially leads to efficient charge-spin interconversion. As the electrical transport property of SrRuO₃ can be readily tuned via structure control, it serves as a platform for studying the manipulation of charge-spin interconversion. Here, a factor of twenty enhancement of spin–orbit torque (SOT) efficiency via strain engineering in a SrRuO₃/Ni₈₁Fe₁₉ bilayer is reported. The results show that an orthorhombic SrRuO₃ leads to a higher SOT efficiency than the tetragonal one. By changing the strain from compressive to tensile in the orthorhombic SrRuO₃, the SOT efficiency can be increased from an average value of 0.04 to 0.89, corresponding to a change of spin Hall conductivity from 27 to 441 × ħ/e (S cm⁻¹). The first-principles calculations show that the intrinsic Berry curvature can give rise to a large spin Hall conductivity (SHC) via the strain control, which is consistent with the experimental observations. The results provide a route to further enhance the SOT efficiency in complex oxide-based heterostructures, which will potentially promote the application of complex oxides in energy-efficient spintronic devices.     

Performance of Layered Steered Space–Time Codes in Wireless Systems

Layered Steered Space–Time Codes (LSSTC) is a recently proposed multiple-input multiple-output (MIMO) system that combines the benefits of vertical Bell Labs space–time (VBLAST) scheme, space–time block codes (STBC) and beamforming. In this paper, we derive the error performance and capacity of a single-user LSSTC system. The analysis is general enough to any layer ordering and modulation schemes used. In addition, the derived analysis is general for any LSSTC structure in which layers may have different number of antenna arrays and may be assigned power according to any power allocation. Furthermore, we analytically investigate the tradeoff between the main parameters of the LSSTC system, i.e., diversity, multiplexing and beamforming. Our results give recursive expressions for the probability of error for LSSTC which showed nearly perfect match to the simulation results. Results have also revealed the possibility of designing an adaptive system in which it was shown that combining beamforming, STBC, and VBLAST has better performance than VBLAST at high SNR range.     

Large PMD Compensated by Four Free Degrees in OTDM System

By introducing a two-stage polarization mode dispersion (PMD) compensator after a optical fiber link with a large PMD,over 270 ps first-order and 2 000 ps2 high-order PMD was compensated. The results show that the two-stage compensator can be used to PMD compensation in the 20 Gb/s optical time division multiplexing system with 60 km high PMD fiber. After compensating, the 270 ps DGD is changed into max. 7 ps. Moreover,the tunable FBG has a function of dispersion compensation.     

Electron Injection Enhancement by Diamond-Like Carbon Film in Polymer Electroluminescence Devices

用正丁胺作碳源,采用射频辉光等离子系统制备类金刚石碳膜(DLC),沉积在聚合物发光器件中的发光层(MEH-PPV)和铝(Al)阴极间作电子注入层.制备了结构为ITO/MEH-PPV/DLC/Al的不同DLC厚度的器件,测量了器件的I-V特性、亮度及效率,研究了DLC层对器件电子注入性能影响的机制.结果表明:当DLC厚度小于1.0nm时,其器件有较ITO/MEH-PPV/Al高的启动电压和低的发光效率;当DLC厚度在1.0～5.0nm之间时,器件的性能随着DLC厚度增加而变好;当DLC厚度为5.0nm时,器件具有最低的启动电压与最高的发光效率;当DLC厚度继续增加时,器件的性能随着DLC厚度增加而变差.并对ITO/MEH-PPV/DLC/Al和ITO/MEH-PPV/LiF/Al的器件性能进行了比较研究.     

Enhancement of Crystalline Quality of Strained Straind InAs／InP Quantum Well Structures by Rapid Thermal Annealing

The effect of rapid thermal annealing of the optical properties of a strained InAs/InP single quantum well structrure has investigated in this paper.The luminescence intensity of the quantum well at 8K was increased by a factor of 4 and 1.55meV blue shoft of the quantum well photoluminescence peak was observed af-ter annealing at the optimal condition of 700℃ for 5s.Furthermoer,we found that the luminescence efficiency of the deep radiative levels in the samples was also affected by rapid thermal annealing.Our experimental results have demonstrated that Rapid thermal annealing significantly improves the erystalline quality of strained quantum well struc-tures after growth and is an important way for enhancement of the performance of the laser device.     

Dispersion of Surface Waves at the Interface between a Dielectric and a Finely Layered Ferrite–Graphene Medium

Journal of Communications Technology and Electronics - The propagation of guided ТМ- and ТЕ-polarized waves along the interface between a dielectric and a finely layered...     

Investigation of Ion-Implanted Photosensitive Silicon Structures by Electrochemical Capacitance–Voltage Profiling

The method of electrochemical capacitance–voltage profiling is used to study boron-implanted silicon structures for CCD matrices with backside illumination. A series of specially prepared structures with different energies and doses of ion implantation and also with various materials used for the coating layers (aluminum, silicon oxide, and their combinations) is studied. The profiles of the depth distribution of majority charge carriers of the studied structures are obtained experimentally. Also, using the Poisson equation and the Fredholm equation of the first kind, the distributions of the charge-carrier concentration and of the electric field in the structures are calculated. On the basis of the analysis and comparison of theoretical and experimental concentration profiles, recommendations concerning optimization of the structures’ parameters in order to increase the value of the pulling field and decrease the effect of the surface potential on the transport of charge carriers are suggested.     

Energy Efficient Mobility Enhancement in LTE Pico–Macro HetNet Systems

Wireless Personal Communications - Unlike terrestrial environment, the underwater environment possess additional and complicated challenges for wireless communication. For the underwater wireless...     

Effect of the Built-in Surface Potential on the I–V Characteristics of Silicon MIS Structures

Russian Microelectronics - The regularities of the modification of I–V characteristics of MIS structures via forming built-in surface potentials induced during the fabrication of an...     

Bioinspired Intelligent Solar-Responsive Thermally Conductive Pyramidal Phase Change Composites with Radially Oriented Layered Structures toward Efficient Solar–Thermal–Electric Energy Conversion

To remedy the drawbacks of weak solar-thermal conversion capability, low thermal conductivity, and poor structural stability of phase change materials, pyramidal graphitized chitosan/graphene aerogels (G-CGAs) with numerous radially oriented layers are constructed, in which the long-range radial alignment of graphene sheets is achieved by a novel directional-freezing strategy. A G-CGA/polyethylene glycol phase change composite exhibits a thermal conductivity of 2.90 W m⁻¹ K⁻¹ with a latent heat of 178.8 J g⁻¹, and achieves a superior solar-thermal energy conversion and storage efficiency of 90.4% and an attractive maximum temperature of 99.7 °C under a light intensity of 200 mW cm⁻². Inspired by waterlilies, solar-responsive phase change composites (SPCCs) are designed for the first time by assembling the G-CGA/polyethylene glycol phase change composites with solar-driven bilayer films, which bloom by day and close by night. The heat preservation effect of the solar-driven films leads to a higher temperature of SPCC for a longer period at night. The SPCC-based solar–thermal–electric generator achieves output voltages of 499.2 and 1034.9 mV under light intensities of 200 and 500 mW cm⁻², respectively. Even after stopping the solar irradiation, the voltage output still occurs because of the latent heat release and the heat preservation of the films.     

Homogeneous–Heterogeneous Hybrid Artificial Photosynthesis Induced by Organic Semiconductors with Controlled Surface Architectures

Photocatalysis is considered an effective approach for converting CO₂ into high-value-added chemicals. However, practical implementation of this technology is limited by the efficiency and stability of photocatalysis. Herein, an interfacial control strategy is proposed to optimize the homogeneous-heterogeneous hybrid photocatalysis by enhancing the interaction between light-harvesting semiconductors (LHS) and molecular active centers (MAC). Based on this strategy, self-assembled organic semiconductors with controlled surface architectures are constructed using 1,6-bis(phenylethynyl)pyrene building blocks to act as LHS. Combining with the classical MAC, an excellent CO₂ photoreduction performance is achieved with a CO turnover number of > 2980 maintaining long-term stability with a selectivity of > 90%, and an apparent quantum yield of > 2.3%. Theoretical calculations combined with in situ and transient spectroscopy studies reveal that the optimized biphase interface dominates the synergy between the homogeneous and heterogeneous photocatalysts. This strategy and the proposed mechanism of interactions will contribute to the design of future artificial photosynthesis systems.     

Physical Principles of Self-Consistent Simulation of the Generation of Interface States and the Transport of Hot Charge Carriers in Field-Effect Transistors Based on Metal–Oxide–Semiconductor Structures

A detailed simulation of degradation (caused by hot charge carriers) based on self-consistent consideration of the transport of charge carriers and the generation of defects at the SiO₂/Si interface is carried out for the first time. The model is tested using degradation data obtained with decananometer n-type-channel field-effect transistors. It is shown that the mutual influence of the above aspects is significant and their independent simulation gives rise to considerable quantitative errors. In calculations of the energy distribution for charge carriers, the actual band structure of silicon and such mechanisms as impact ionization, scattering at an ionized impurity, and also electron–phonon and electron–electron interactions are taken into account. At the microscopic level, the generation of defects is considered as the superposition of single-particle and multiparticle mechanisms of breakage of the Si–H bond. A very important applied aspect of this study is the fact that our model makes it possible to reliably assess the operating lifetime of a transistor subjected to the effects of “hot” charge carriers.     

Limitations of Control of Electrophysical Characteristics of Quantum-Size Structures by Electrochemical Capacitance–Voltage Profiling

Journal of Communications Technology and Electronics - A method is proposed to control the distribution of carrier concentration over the profile of multilayer heteroepitaxial structures (HESs)...